This invention relates to a fluidized bed reactor and, more particularly, to such a reactor in which heat is generated by the combustion of particulate fuel in a fluidized bed.
Fluidized bed reactors, usually in the form of combustors, boilers, gasifiers, vaporizers, or steam generators, are well known. In a normal fluidized bed arrangement, air is passed through a perforated plate, or grate, which supports a bed of particulate material, usually including a mixture of fuel material, such as high sulfur bituminous coal, and an adsorbent material for the sulfur released as a result of the combustion of the coal. As a result of the air passing through the bed, the bed behaves like a boiling liquid which promotes the combustion of the fuel. In addition to enjoying a high capability for reducing the amount of sulfur in the combustion gases introduced to the atmosphere, such an arrangement permits relatively high heat transfer rates per unit size, substantially uniform bed temperatures, relatively low combustion temperatures and reduction in corrosion and boiler fouling.
In many applications of the fluidized bed process, and especially in connection with combustion and reaction processes, heat absorbing-steam generating enclosure walls are provided which are formed by a plurality of interconnected water tubes through which water is passed to pick up heat from the fluidized bed and convert the water to steam. In these cases, the fluidized bed must be designed to operate within close temperature limits requiring the installation of heat absorbing surfaces, usually in the form of additional coils, or tube bundles, installed in the bed, since considerably more heat must be removed from the bed than can be removed by the enclosure walls. It is conventional practice to provide separate individual feeders to, and risers, or the like, from each wall section and steam generating tube bundle circuit independently. However, the complexity and cost of this separate circuiting (with associated individual tubing, piping, headers, enclosure wall penetrations, drum penetrations, weldments, supports, insulation and lagging) can be significant, particularly where large differences in elevation exist between circuit inlets and the steam drum or circuit outlets.